The R-2R resistor ladder dac --> ADC test was disabled due to a bug in
the v0.1 version of the shield. Since this has been fixed in v0.2 and
v0.3 of the shield, it can be re-enabled.
The comment regarding the high accuracy of the resistor is dropped, as
v0.3 has been ordered with cost efficient resistors rather than with
accurate ones. As a result, the tolerance for error has been increased
to 10%. This quite a bit more lax than I have hoped for, but false
positives would be something to avoid.
The test should execute only with `make test-with-config` and not with
`make test`, as boards without the shield cannot pass the test.
For some reason I accidentally added both variants, which makes no
sense. This drops the `make test` variant.
Finally, the `README.md` is updated to refer to `make test-with-config`
instead of `make test`.
This test application makes use of the RIOT Peripheral Selftest Shield,
which connects e.g. PWM to ADC or SPI MOSI to SPI MISO, UART TXD to RXD,
etc. This provides quick and fully automated self testing capabilities.
Please note that the simplicity and ease of use of the hardware comes
with a prices: There are whole classes of issues that cannot be detected
automatically. This test cannot replace other testing approaches
(such as manual testing or PHiLIP on the HiL), but only complement them.
To detect misconfigurations of addresses and sizes, the whole memory is filled word-wise with it's addresses. If the content doesn't match, it prints the address and the content.
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